Hydraulic resistor



INVEN TORS ATTO R N EY S mmkui J. E. SMITH ET AL HYDRAULIC RESISTOR DIFF. PRESSURE GUAGE RETURN LINE JOHN E. SMITH BY ROBERT S.FLEM|NG ALTON G.DeCLAlRE,JR. G ORG B. STROH RESISTOR BACK TO PUMP VIA. SUPPLY TANK 1 w a. H 2 R V w \J/PX S mm H? W mm 2 Sept. 20, 1960 Filed Aug. 22, 1955 FIGJ.

Sept. 20, 1960 J. E. SMITH ET AL HYDRAULIC RESISTOR Filed Aug. 22, 1955 5 Sheets-Sheet 2 4mm 2- wmsmwwma qfihzumuuma aq N O. m m k. w m v m O N ENTORS JOHN E.SM!TH 2O mkmm z mm mm OO 2: mmo;

ALTON G.DeCLAIRE,JR.

EORGE B. TROH V ATTORNEYS wdE 5 SheetsSheet 3 Filed Aug. 22, 1955 HFIOH 83d SGNnOd ROBERT SELEM ALTON 6.0601] United States Patent "ice HYDRAULIC RESISTOR John E. Smith and Robert S. Fleming, Detroit, Alton G. De Claire, Jr., Harper Woods, and George B. Stroh,

, Detroit, Mich., assignors to Holley Carburetor 'Company, Detroit, Mich., a corporation of Michigan Filed Aug. 22, 1955, 'Ser. No. 529,730

9 Claims. (Cl..138--40) The present inventon relates to a hydraulic resistor.

It is an object of the present invention to prow'de a hydraulic resistor effective to have a predetermined impedance to liquid flow therethrough.

.More specifically, it is an object of the present invention to provide a hydraulic resistor which may be selectively set to have laminar flow resulting in liquid flow directly proportional to differential pressure across the resistor, or to have transitional flow (that is, a flow intermediate in characteristics between laminar flow and true turbulent flow).

It is a further object of the present invention to provide a hydraulic resistor including a plurality of passages and associated therewith means for controlling the nature of flow through the several passages so as to produce an overall predetermined impedance to flow.

It is a feature of the present invention to provide a hydraulic resistor including means forming one or more cylindrical passages adapted to be connected into a hydraulic flow line in association with pin means received in each of said cylindrical passages havingits diameter so related to the internal diameter of the passage with which it is associated as to produce a desired type of liquid flow therethrough.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view through a hydraulic resistor.

Figure 2 is a sectional view on the line 22 Figure 1.

Figure .3 is a diagrammatic view, showing the connection of the hydraulic resistor into a hydraulic circuit.

Figure 4 is a, chart showing flow plotted against differential pressure when employing the hydraulic resistor.

Figure 5 is a diagram showing the manner of determining values of the exponent m;

ln many cases, in running tests involving liquid flow as for example, in testing carburetors or the like, it is important to provide a hydraulic resistor having a known predetermined and preferably adjustable resistance to iq i w- 'Basically, it has been found that true laminar flow, in which the flow of liquid is directly proportional to the pressure drop across the resistor, can be provided in a simple and effective manner by employing a true cylindrical passage having a true cylindrical pin received in the passage, the diameter of the pin being slightly smaller than the internal diameter of the cylinder to simulate leakage between a piston and sleeve.

By controlling theclearance, length and difierential pressure applied across the resistor, the flow can be made truly'laminar in which W (the flow of fuel or liquid) is directly proportional to AP (differential pressure).

2,953,167 Patented Sept. 20, 1960 0.5. The same equation follows for laminar flow where,

the exponent m is equal to 1.0. With the present hydraulic resistor it is possible to produce flow represented by the same equation in which the exponent m has any desired value greater than 0.5 and not more than 1.0. Moreover, by employing a plurality of passages and pins in parallel it is possible to produce a hydraulic resistor offering substantially any desired impedance to flow.

Referring now to the drawings, a simple form of hydraulic resistor constructed in accordance with the present invention is illustrated in Figures 1 and 2; The resistor comprises a casing consisting of a cup-like body 10 and a removable cap or closure 12. The cup-like body 10 is provided with a cylindrical chamber 14 open at one end of the body and provided at its opposite end with a reduced extension 16. The end of the body 10 adjacent the extension 16 is closed except for a passage 18 adapted to serve as an outlet connection for the resistor. Intermediate from the ends of the cylindrical chamber 14 is an outwardly extending annular channel 20 for a purpose which will presently appear.

The removable cap or closure 12 is provided with a passage 22 serving as the inlet connection for the resistor. The cap 12 is provided with an annular shoulder 24. The cap 12 is retained in sealed relation to the body 10 by suitable means such for example as fastening screws26 and the gasket indicated at 28.

Located within the interior of the casing is a compound cylinder indicated generally at 30 having a cylindrical portion 32 received in the cylindrical chamber 14 and having a reduced cylindrical extension 34 received in the reduced extension 16 of the chamber 14. The dimension of the cylindrical portion 32 is such that its ends are adapted to be engaged by the annular shoulder 24 of the cap and an annular shoulder 36 formed by the reduced extension 16 of the chamber 14. Thus, the cylinder 30 is retained against substantial axial movement within the casing.

In assembly suitable sealing means such for example as the O-ring indicated at 38, is received in the channel 20 and provides an eifective seal between opposite ends of the cylinder 30. The cylinder 30 is provided with a plu rality of accurately sized and finished cylindrical openings 40, all of which are preferably of the same identical size. In assembling the hydraulic resistor, pins 41 are located in the cylindrical passages 40. These pins preferably are of a length sufiicient to extend between the adjacent surfaces of the cap 12 and the end surfaces of the reduced extension 16 of the chamber as illustrated. In addition, the pins are accurately dimensioned as will subsequently be described in detail. With the parts assembled as illustrated in Figure 1, it will be observed that the liquid inlet connection 22 communicates with an inlet header space 42, and an outlet header space 44 connects the outlet ends of the cylindrica-l passages 40 to the outlet passage 18. Passages 46 and 48 respectively extend from the exterior of the casing to the header spaces 42 and 44.

Referring now to Figure 3 there is diagrammatically illustrated an arrangement in which the hydraulic resistor is connected in a hydraulic circuit as labeled on the figure. It will be observed that a differential pressure gauge is connected across the test fixture and has com duits 50 and 52 by means of which it is connected to the passages 46 and 48 of the hydraulic resistor.

The outlet of the gear pump is variably controlled by an adjustable valve V so as to provide the required pressure drop AP across the hydraulic resistor. The actual flow of liquid through the resistor is measured by the meter. e V

The resistance or impedance to flow afforded by the hydraulic resistor is determined by the number of cyline drical' passages 40 which are open to flow and. by the, dimensions of the pins 41 received therein. Inthe illustrated embodiment of the present invention four of the cylindrical passages are provided although of course a much larger number could be provided if desired. If. it is desired'to reducethe overall flow of fluid any number of the cylindrical passages 40, maybe plugged.

In general, true laminar flow takes place through a passage 40 containing a restricting pin 41 when the diameter of the pin is close. to. the internal diameter ofthe opening. If. the diameter of the pin is reduced in size, flow, intermediate between laminar and turbulent flow'takes place, ,and in the present instance this flow is referred to as transitional flow. 7

Referringmagain to the formula W =KAP flow. in accordance with this formula is said to be turbulent when the. valueof the exponent m is equal to 0.5, flow is said tobe laminar when the value of the exponent m is.1.0,- a'nd in accordance withthe description herein flow said. to be transitional when the value ofthe exponent mgreater than 0.5' but lessthan 1.0

The, present apparatus, permits the production. orad-.

-that the use'of two passages using identical pins ofa certain size satisfies therequirements except that the value of the exponent mis slightly less than desired. Substi-. tution of the next larger size 'of'pins produces a value of theexponent m which is slightly larger than desired. In

4 flow. When the smoke is diffused and breaks up it is turbulent flow. The controlling factor of the nature of flow is the Reynolds number. The Reynolds number for flow through a circular pipe is:

NR=V' where:

The clearance between the piston and sleeve is b, the diameter'of the piston is D, and the length is L. Certain values of .b, L and AP assure laminar flow. The hydraulic. resistor of Figures 1 and 2 has, been designed to embody these principles in a practical device. A fixed number of small holes have been drilled in the fixture and pins; are inserted in the holes. The flow area, a func-. tion of b, can becontrolled closely by the size of the pins. The same flow area could be obtained by drilling very small holesbut the,size;needcd is so small that it would not be practical, to attempt drilling the hole Referring now -to Figure 4, the flow is laminar when the plot of W against AP is linear. As the diameter of 2 the pins decrease. the clearance increases, and the curve order to produce a value of m close tothe desired value,

one pin of the larger size'will be provided: in one passage and a pin of the smaller size will be provided in the remaining passage. 7 This will have the efiect of producing a value of the exponent m substantially midway between the values previously obtained. by: the use of. identical pins. In thesame mannenif it is desirable to increase total flow (or increase the value of K in the equation), this maybe accomplished by employing morepassages. In the specific example previously described, two.addi-. tional passages could be employed using pins of the two different sizes referred to in the foregoing.

From the foregoing it will be. observed that by. proper selection of the number of passages and size of pins, the hydraulic resistor may be assembled or adjusted to producea wide range of fiuid'flow resistance. r

Referring now to Figure 4 there is illustrated a chart showingvalues obtained in ahydraulic resistor. provided with four cylindrical passages and in. which all of the passages are provided withpins, Each of the curves obtained shows the diameter. of the pin or pins. and it will be observed that in some cases all ofthe pins; are

varies, more and more from a straight line, indicating the flow is changing from laminar to turbulent. When the flow -is laminar, WfocAP, but'for turbulent flow W aAP There is a transition phase between laminar and turbulent flow where W aAP with .1 m /2., The

' valueof m is found by plotting W5 versus AP on log log graph paper and measuring the slope of the line. (W{=KAP log W m.log KAP,-y==mx, m is 'slope'of line.) This is shown in Figure S'for seven sets of pins, varyingffrom. 0.060'-diameter to 0.047 diameter. .The resulting plot is a series of straight lines with the slope of' a line equal to the exponent of AP for that particular. set of pins. The values of; m and the diameters of the pins used to make seven sets are found in Figure 5.

For any value of AP, in the hydraulic resistor range,

V value of W, can be obtained;

One method is to increase the fuel 'flow by increasing the. number of holes reamed into the cylinder. Using the cylinder described in Figure '1, with,.063" diameter holes and a wall thickness of .050", the maximum number of vholes that can be reamed'inthe cylinder is ten.

Another; method of changing the fuel flow can also be obtained by changing the size of the pins. ,For example, a value: W for' a specific AP might be needed that; is midwayv between the r/ alues obtainedjby using of the same size and in other cases pins. of twodifierent sizes are employed. 1 In this; case the internal diameters of the cylindrical passages are .063 and the length of passages is .500". As will be observed from the chart,

' thecurves obtained are the'result of plotted,AP. (differentialv pressure in pounds per square inch) against W 7 (measured in this instance in'pounds per hour).

The present invention is base upon a recognition of the fact: that hydraulic flow is ordinarily: described as of twoQtypes, laminar and'turbulent.

7 These can be illus= trated'bywatching smoke rise fromfa cigarette in1a still room. The smoke rises undisturbedin l'aminaeor layers 1 'for a short distance above the cigarette. This islaminar sets of 0.056T'and 0.057" pins. Then a set would be made of-half 0.056" pins: and half 0.057"pins,' which will give W very close; togthe value wanted. Fine adjustmentfcan be made by; inserting smaller or larger pins. Byinterchangingthe pins; the value of W, forany AP can be;contr0lled veryclosely. In other words, this procedure; demonstrates that. this design is infinitely adjustable; j a V V .For the .060" diameter pins the plot of W;;ver sus Al? is linear, indicatinglaminarflom ,The' plots for the .058" diameter pins to'the. .0545" diameter pins deviate slightly froma s'traightlirie, indicatingatransitionphase betweenxlaminarand turbulentflow. The plots. ofithe .0545" pins to the .045" pins show that the flow is more in a turbulent phase than it is laminar.

The exponent of AP, which is an indication of the nature of the flow, can be found in Figure 5. The slope of the curve, W; versus AP plotted on log log graph paper, is the exponent of AP. This value varies from .949 for the .060" diameter pins to .600 for the .047" diameter pins. Thus, the slopes of all the curves are greater than .500, so the flow is not entirely turbulent but in the transition phase. j

The drawings and the foregoing specification constitute a description of the improved hydraulic resistor in such full, clear, concise and exact termsas to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What we claim as our invention is:

1. A hydraulic resistor having inlet and outlet connections and 'a plurality of cylindrical passages of the same internal diameter having open ends in communication with said connections, a cylindrical pin in each of said passages and extending the full length thereof, some of said pins being of diiferent diameters, each of said pins having a uniform diameter smaller than but sufficiently close to the internal diameter of the passage in which it is located to produce a liquid flow therethrough represented by W;=KAP where W is liquid flow, K is a constant, AP is the pressure differential across said resistor, and the exponent m has a value greater than 0.5 but not more than 1.0.

2. A hydraulic resistor comprising a casing having inlet and outlet connections and an enlarged chamber therein, a body in said chamber having a plurality of identical cylindrical passages therethrough, said casing comprising a removable cap to provide access to said body, and sets of pins of different accurately predetermined sizes extending completely through said passages to determine the nature of fluid flow therethrough to provide for selective control of flow characteristics.

3. A hydraulic resistor comprising a housing having a main chamber open at one end and having a reduced chamber portion extending beyond the other end of the main chamber, a removable cap covering the open end of said main chamber and having a recess of cross-section smaller than that of said main chamber, a body in said main chamber having end abutment portions larger than said reduced chamber portion and recess to space the ends of said body from the bottom of said reduced chamber portion and recess, said body having a plurality of cylindrical passages of equal diameter extending therethrough, and pins in said passages having a length greater than the length of said passages to cause the ends of said pins to extend beyond the ends of said passages into said reduced chamber portion and recess, sealing means between said body and main chamber, and passage means communicating with said reduced chamber portion and recess.

4. An adjustable hydraulic resistor comprising a housing having a main chamber open at one end and having a reduced chamber portion extending beyond the other end of the main chamber, a removable cap covering the open end of said main chamber and having a recess of cross-section smaller than that of said main chamber, a body in said main chamber having end abutment por tions larger than said reduced chamber portion and recess to space the ends of said body from the bottom of said reduced chamber portion and recess, said body having a plurality of cylindrical passages of equal diameter extending therethrough, a plurality of pins of uniform diameter located in said passages and extending beyond the ends thereof, the diameters of different pins being of different size, said pins being selected to produce a flow across said resistor which is intermediate laminar to turbulent.

5. An adjustable hydraulic resistor comprising a housing having a main chamber open at one end and having a reduced chamber portion extending beyond the other end of the main chamber, a removable cap covering the open end of said main chamber and having a recess of cross-section smaller than that of said main chamber, a body in said main chamber having end abutment portions larger than said reduced chamber portion and recess to space the ends of said body from the bottom of said reduced chamber portion and recess, said body having a plurality of cylindrical passages of equal diameter extending therethrough, a plurality of pins of uniform diameter located in said passages and extending beyond the ends thereof, the diameters of different pins being of different size, said pins being selected to produce a flow across said resistor which is intermediate laminar to turbulent, some of said passages being plugged to control total volume of flow.

6. A hydraulic resistor having inlet and outlet connections and a plurality of accurately dimensioned cylindrical passages of uniform identical diameter having open ends in communication with said connections, a plurality of removable and replaceable pins received in said passages, said pins being longer than said passages and of different diameters, each of the pins being of uniform diameter smaller than but sufiiciently close to the diameters of said passages to produce liquid flows therethrough, when pins are received in said passages, the diameters of the different pins being such as to cause a fiow across the resistor which is represented by Wf=KAP where W, is the liquid flow, K is a constant, and AP is the pressure differential across the resistor, in which the exponent m has a value intermediate 0.5 and 1.0.

7. A hydraulic resistor having inlet and outlet connections and a plurality of accurately dimensioned cylindrical passages of uniform identical diameter having open ends in communication with said connections, means comprising removable and replaceable cylindrical pins 7 received in said openings to determine the nature of hydraulic flow therethrough, said pins being of such difierent selected sizes relative to the passages in which they are received that flow across said resistor is represented by the formula W =KAP Where W; is flow, K is a constant, AP is the pressure difierential across the resistor, and in which the exponent m has a value intermediate 0.5 and 1.0.

8. A hydraulic resistor having inlet and outlet connections and a plurality of cylindrical pass-ages of known diameter connected in parallel between said inlet and outlet connections, a removable and replaceable cylindrical pin of known diameter received in each of said passages, each of said pins having a diameter less than the diameter of the passage in which it is received to determine the nature of the hydraulic flow therethrough, the difierence in diameters between at least one of said passages and the pin received therein being difierent from the difference between the diameter of another of said passages and the pin received therein, the differences in passage and pin diameters being such as to cause a flow across the resistor which is represented by W =KAP where W; is the liquid flow, K is a constant, and AP is the pressure differential across the resistor, in which the exponent m has a value intermediate 0.5 and 1.0.

9. In a hydraulic resistor for controlling mass flow rate in accordance with the formula W =KAP where W, is mass flow, K is a constant, AP is the pressure head and the exponent m is the logarithmic slope of the curve defining the mass flow rate through said resistor for varying values of AP, and having a plurality of accurately dimensioned cylindrical passages of uniform known diameter for conducting said mass flow,

7 8 means for selectively varying the value of m between is intermediate the values of massflow which would 0.5{and 1.0,; said means, epmp'ris ing a plurality of reresult from strictly laminar and strictly turbulent flow. mq bte. andr r n ieceablq cy i P 7 1 f diameters a -r e ved;wi hi1 o p h said 7 References- Cited i the file this pat ent eyl i-ndrieak passages to restrict mass flow therethrough, 5 UNITED SDSLTES.w PATENTS the. difier egce' in diameters between at. least one of said nass ages; and the pin received therein being different 2,037,994 lfi auer Apr. 21,-, 1936- lfrqm. the difierencebetweenthe; diameter between an; {2,323,115 Q-E n 29, 1943' other of said passages and the pin received therein the 4 i 20, 1946 in passageand pin diameters being such as 19 2,546,078 Adams 3 1953 to pr duce a mtal: mass flow ihrepgh {the resistor which 2,675,603 K011511133 p 27, 1954' 

